The present invention relates to liquid stirrers, and relates more particularly to a pressure-differential liquid stirrer which stirs up the liquid by continuously driving compressed air into the liquid tank and then releasing compressed air from the liquid tank.
Various liquid stirrers have been developed for use in chemical, dyestuff, and food industries to stir different liquids. These stirrers commonly use magnetic force, propelling force, or bubbles to stir liquids. FIG. 1 shows a conventional magnetic stirrer which comprises a liquid tank, a magnetic stirring stick placed inside the liquid tank, a motor disposed below the liquid tank, and a magnet coupled to the output shaft of the motor and turned to move the magnetic rod in the liquid tank. This structure of liquid stirrer is not suitable for a high speed stirring operation, therefore it is commonly used in stirring liquids of low viscosity. If the magnetic stirring stick or the magnet loses its magnetic force, the stirring work becomes unable to be achieved. FIG. 2 shows the structure of a conventional propeller stirrer which comprises a liquid tank, a motor suspended from a support outside the liquid tank, and a propeller disposed inside the liquid tank and turned by the motor to stir the liquid. The main drawback of this structure of liquid stirrer is its complicated procedure of replacing the liquid. Furthermore, this structure of liquid stirrer is not practical for an enclosed stirring operation. FIG. 3 shows the structure of a conventional bubble stirrer which comprises a liquid tank, an air pipe having one end inserted into the inside of the liquid tank and an opposite end connected to an air compressor. When compressed air is driven from the air compressor into the liquid tank through the air pipe, bubbles are produced in the liquid inside the liquid tank, thereby causing the liquid to be stirred. This structure of liquid stirrer is simple in structure and less expensive. However, because bubbles are produced in the liquid, the quality of the liquid may be affected.